This invention is in the field of heat transfer and cooling of semiconductor chips used in computer and telecommunication equipment. More particularly, this invention is directed to the constructing of a cooling device for semiconductor circuit chips soldered or socketed on a common carrier such as a printed-wiring board or multichip module, and for a method of assembly of such a device and with the devices to be cooled.
The problem that this invention intends to solve is an improved heat conduction device to carry heat from a plurality of heat generating semiconductor devices on a common carrier. The size and height of the semiconductor devices vary as well as the top surfaces of the semiconductor devices are also not in the same plane.
Specifically, in the case of semiconductor integrated circuits, the circuit chips are interconnected to the next level of printed-wiring card/boards assembly using any type of chip packaging methods such as column, ball, or land grid arrays. The variation of the height among the many interconnecting elements can be as large as 0.25 mm. Such variations can cause uneven surface requirements for a common cold plate or heat sink solutions mentioned in previously issued patents. Such patents includes the following U.S. Pat. Nos. 5,239,443, 5,309,319, 5,023,6959 5,294,830, 5,170,319, 5,420,753, 5,537,291, 5,016,090, 6,111,749, 5,052,481, and 4,498,530.
It is therefore an object of the present invention to provide a cooling device for semiconductor circuit chips soldered or socketed on a common carrier such as a printed-wiring board or multichip module.
It is a further object of the invention to provide a method of constructing such a cooling device.
The exemplary cooling device according to the invention may comprise one coolant distribution unit and multiple compliant cooling elements in contact with multiple semiconductor chips on a common carrier. The invention uses a flexible structure inside the coolant distribution unit coupling with the cooling elements to provide the needed compliance when the cooling elements are in contact with the semiconductor chips. Mechanisms are included in the cooling device to prevent coolant leakage to the outside of the cooling device. Flexible concentric tubing may be used to deliver and collect coolant from the cooling elements while providing the needed compliance.
In accordance with the invention, an apparatus for cooling a plurality of devices, comprises a bottom plate; a cover; a first flexible member supported in the cover, the first flexible member having first openings therein; a second flexible coolant blockage member supported between the cover and the bottom plate, the second flexible coolant blockage member having second openings aligned with the first openings; respective cooling elements having first portions extending through the first openings and second portions extending through the second openings, each of the cooling elements having a cooling surface for contacting a device to be cooled; coolant tight seals for sealing the first portions of the cooling elements to the support member and the second portion of the cooling elements to the coolant blockage member; and coolant flow channels formed in the cover and the cooling elements to allow flow of coolant to cool the cooling elements.
The apparatus can further comprise a mechanical bias element for biasing the cooling elements away from the cover. The cooling elements may further comprise a motion stop portion for interacting with the bottom plate to limit movement of the cooling element away from the cover caused by the bias element. The cover may comprise a cover plate; and a frame member, the first flexible member being supported between the cover plate and the frame member.
The coolant flow channels in each cooling element include an opening for receiving cooling fluid from the cooling channels in the cover, a serpentine coolant flow passage adjacent the surface contacting the devices to be cooled, and a coolant outlet passage for discharging coolant to flow through an outlet passage in the cover. The cooling elements comprise a first part having a series of fins and a second part having a series of grooves. The grooves in the first part and the groves in the second part mate together to form a serpentine channel for the passage of coolant.
The coolant tight seals comprise first annular grooves in the first portions of the cooling elements and second annular grooves in the second portions of the cooling elements; and first annular projections extending from the first flexible member into the first annular grooves, and second annular projections extending from the second flexible member into the second annular grooves. The coolant tight seals may further comprise annular seal bands surrounding portions of the first flexible member and portions of the second flexible member in proximity to the projections.
The second flexible member, the bottom plate, and the cooling elements may define cavities or chambers in which coolant absorbent material may be placed. The coolant absorbent material may be selected from any type of desiccants such as silica gel, calcium aluminosilicate, polyacrylamide, etc.
The apparatus may be combined with a carrier having thereon a plurality of devices to be cooled, at least some of the devices being disposed on the carrier so as to come into contact with the cooling surfaces of the cooling elements.
The invention is also directed to an apparatus for cooling a plurality of devices, comprising a housing; a bottom plate disposed in the housing, the bottom plate having first openings therein; a cover plate for closing the housing; a second plate supported in the housing between the bottom plate and the cover plate to define a first space between the cover plate and the second plate and a second space between the second plate and the bottom plate, the second plate having second openings therein, the second openings being aligned with respective first openings; an outer cooling element for contacting each of the devices to be cooled; an outer tube for connecting each of the outer cooling elements to the bottom plate, each of the outer tubes being received in a respective one of the second openings; an inner cooling element received within the outer cooling element, each of the inner cooling elements having a connecting opening; an inner tube within each of the outer tubes for connecting each of the second cooling elements to the second openings so as to define a flow space between the inner tube and the outer tube; whereby a path for flow of coolant is defined extending along the first space, the inner tube, the connecting opening, the flow space, and the second space.
The second openings have an enlarged region to define an annular space between the outer tube and the bottom plate. The apparatus further comprises a seal disposed between the outer cooling element and a wall of the enlarged region so as to close the annular space. A coolant absorbing material may be disposed in the annular space. The coolant absorbent material is selected from any type of desiccants such as silica gel, calcium aluminosilicate, polyacrylamide, etc.
The outer cooling elements and the walls of the opening may each be configured with corresponding annular grooves, and the seal comprises an O-ring having portions disposed in the grooves. The inner tubes and the outer tubes are comprised of a resilient material.
The invention is also directed to a method of assembling a cooling apparatus to a carrier having devices to be cooled. The method comprises partially evacuating at least one chamber in the cooling apparatus so as to move cooling elements in a direction and to a position wherein cooling surfaces of the cooling devices can not contact the devices when the cooling apparatus and the carrier are assembled; placing the cooling apparatus over the carrier; and allowing fluid to enter the at least one chamber so that the cooling surfaces are forced into contact with the devices.
The cooling apparatus may be placed over the carrier by sliding the cooling apparatus and the carrier with respect to one another in a direction parallel to a plane of the carrier.